Submount substrate for mounting light emitting device and method of fabricating the same

ABSTRACT

A submount substrate for mounting a light emitting device and a method of fabricating the same, wherein since a submount substrate for mouthing a light emitting device in which a Zener diode device is integrated can be fabricated by means of a silicon bulk micromachining process without using a diffusion mask, some steps of processes related to the diffusion mask can be eliminated to reduce the manufacturing costs, and wherein since a light emitting device can be flip-chip bonded directly to a submount substrate for a light emitting device in which a Zener diode device is integrated, a process of packaging the light emitting device and the voltage regulator device can be simplified.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of prior U.S. patentapplication Ser. No. 11/174,640 filed Jul. 6, 2005, which claimspriority under 35 U.S.C. §119 to Korean Application No. 10-2004-0053640filed on Jul. 9, 2004, whose entire disclosure is hereby incorporated byreference.

BACKGROUND

1. Field of the Invention

The present invention relates to a submount substrate for mounting alight emitting device in which a Zener diode used as a voltage regulatordevice is integrated, and a method of fabricating the same. Moreparticularly, the present invention relates to a submount substrate formounting a light emitting device in which a PN Zener diode or a Zenerdiode having a bi-directional threshold voltage characteristic isintegrated using a silicon bulk micromachining process, and a method offabricating the same.

2. Description of the Related Art

In general, a light emitting device such as a light emitting diode or alaser diode using a group III to V compound semiconductor material of adirect transition type semiconductor can generate a variety of coloredlights including green, blue, ultraviolet and the like as a result ofdue to the advancement in the field of thin film growth technologies andsemiconductor materials.

Furthermore, a white light with good efficiency can also be embodied byusing a fluorescence material or combining a variety of colors.

The technological advancement thus described enables, the light emittingdevice to encompass a wide range of applications such as a transmissionmodule for optical-communication system, an light emitting diode (LED)backlight capable of substituting for the cold cathode fluorescence lamp(CCFL) constituting the backlight of a liquid crystal display (LCD)device, a white LED system capable of substituting for a fluorescentlamp or incandescent lamp, and a traffic light, in addition to a displaydevice.

FIG. 1 is a cross-sectional view of a general LED device. In order tofabricate this LED device, a buffer layer (102), an n-contact layer(103), an n-cladding layer (not shown), an active layer (104), ap-cladding layer (not shown), and a p-contact layer (105) aresequentially deposited on the top of a substrate (101) made of sapphire,n-GaAs, GaN or the like, using a chemical vapor deposition process.

Thereafter, a mesa etching is carried out to expose the n-contact layer(103), through a photolithographic etching process and a dry/wet etchingprocess.

Next, on the top of the p-contact layer (105) is formed a currentdiffusion layer (106), which is formed of a transparent electrode withgood light transmission. For an electrical connection with an externalcircuit, a p-electrode (107-p) and an n-electrode (107-n) are formed onthe current diffusion layer (106) and the n-contact layer (103),respectively, thereby forming a LED device (100).

In other words, when a voltage from an external circuit is appliedbetween the p-electrode (107-p) and the n-electrode (107-n) in thelight-emitting device, positive holes and electrons are injected intothe p-electrode (107-p) and the n-electrode (107-n). While the positiveholes and the electrons are recombined in the active layer (104), extraenergy is converted into light, which in turn is emitted to the outsidethrough the current diffusion layer and the substrate.

In the meantime, if static electricity or surge voltage is produced inthis type of light emitting device, an excessive electric charge flowsinto the semiconductor layers and finally causes failure of the lightemitting device.

This problem becomes worse in a case where the devices are fabricated onthe top of a dielectric substrate. When the surge voltage is produced inthe device, an applied voltage may rise up to a few thousands volts.Thus, when a light emitting device has a low withstand voltage(allowable voltage), an additional protective device should beinstalled.

As a protective device, for example, a plurality of general diodes areconnected in series such that the diodes can be turned on at a voltagehigher than the driving voltage of the light emitting device.

Therefore, as shown in FIGS. 2 a and 2 b, a PN or PNP (NPN) Zener diode(200. 300), which is used as a constant voltage device, is connected toa light emitting device (100) in such a manner that their oppositeelectrodes are connected to each other. Thus, the voltage applied to thelight emitting device is restricted to Vz (Zener voltage) of the Zenerdiode.

If the reverse voltage of the Zener diode is equal to or greater thanVz, the reverse current (a current flowing from the n-electrode towardsthe p-electrode) increases and the terminal voltage between both ends ofthe Zener diode remains almost constant, i.e. Vz.

In this way, a Zener diode is not only used as a protective device butalso widely used as a voltage regulator device for maintaining a loadvoltage to be constant against variation in an input voltage or in aload.

Such a Zener diode as a protective device is fabricated separately fromthe device, such as a light emitting device, to be protected and is thenelectrically connected thereto in parallel. Alternatively, the lightemitting device and the Zener diode may be connected on a siliconsubmount substrate by means of a flip chip bonding.

FIGS. 3 a to 3 g are cross-sectional views explaining a process offabricating a conventional PN Zener diode. FIGS. 3 a and 3 b show aprocess of forming masks.

First, a Zener diode is a device that utilizes the tunneling effect inquantum mechanics, and thus, a substrate (201) with low resistance mustbe used. Since Zener voltage (Vz) of the device is determined by theelectrical resistivity of the substrate and the concentration ofdiffused impurities thereof, a substrate with an appropriateconcentration of impurities contained therein must be used (see FIG. 3a).

Further, in order to selectively diffuse impurities into the substrate,a diffusion mask (202) (a silicon oxide film generally employed) isdeposited on the top and bottom surfaces of the substrate. Then, thediffusion mask deposited on the top surface of the substrate isselectively etched and then patterned (see FIG. 3 b).

FIG. 3 c shows a diffusion step. After patterning the diffusion mask, adiffusion process is carried out. Impurities different from those in thesubstrate are injected into the substrate through a portion (portion “B”of FIG. 3C) where the diffusion mask is etched. The impurity injectionprocess can utilize a diffusion process and an ion injection processusing a furnace.

Here, impurities are not injected into the substrate through a portion“A” where the diffusion mask remains, because the impurities are coveredby the diffusion mask.

Thereafter, the diffusion mask is removed (see FIG. 3 d), and aprotective film (203) is deposited on the top surface of the substrate(201). Then, the diffusion area D of the substrate (201) is exposed (seeFIG. 3 e).

Finally, as shown in FIGS. 3 f and 3 g, on the top surface of theexposed diffusion area (D) of the substrate (201) is formed an electrode(204-f)), and on the bottom surface of the substrate (201) is formed anelectrode (204-b). Consequently, a Zener diode (200) is fabricated.

As described above, the Zener diode according to the prior arts requiresseveral processes such as a diffusion mask deposition process, adiffusion mask photo process and a diffusion mask etching process.Accordingly, there is a problem in that manufacturing costs can not bereduced due to increased the number of manufacturing processes.

SUMMARY OF THE INVENTION

The present invention is conceived to solve the aforementioned problem.Accordingly, an object of the present invention is to provide a submountsubstrate for mounting a light emitting device and a method offabricating the same, wherein the submount substrate for mounting thelight emitting device in which a Zener diode device is integrated can befabricated by means of a silicon bulk micromachining process withoutusing a diffusion mask, thereby reducing processes related to thediffusion mask and thus reducing manufacturing costs.

Another object of the present invention is to provide a submountsubstrate for mounting a light emitting device and a method offabricating the same, wherein a process of packaging the light emittingdevice and a voltage regulator device can be simplified by flip-chipbonding the light emitting device directly to the submount substrate forthe light emitting device in which a Zener diode device is integrated.

According to a first aspect of the present invention for achieving theobjects, there is provided a submount substrate for mounting a lightemitting device, comprising: a substrate doped with first polarimpurities; a first diffusion layer formed by causing second polarimpurities having the polarity different from that of the first polarimpurities to be injected and diffused into the substrate, and thendivided into two parts by means of a substrate region with no diffusionregion formed thereon; an insulating layer formed on a top surface ofthe substrate and having a first opening through which a part of onedivided region of the first diffusion layer is exposed and a secondopening through which a part of the substrate region with no diffusionregion formed thereon is exposed; a first electrode line formed on a topsurface of the insulating layer and connected to the first diffusionlayer through the first opening; and a second electrode line connectedto the substrate region through the second opening.

According to a second aspect of the present invention for achieving theobjects, there is provided a submount substrate for mounting a lightemitting device, comprising: a substrate doped with first polarimpurities; a first diffusion layer formed by causing second polarimpurities having the polarity different from that of the first polarimpurities to be injected and diffused into the substrate and thendivided into two parts by a first region with no diffusion region formedthereon, each divided diffusion layer being divided into two parts by asecond region with no diffusion region formed thereon; an insulatinglayer formed on a top surface of the substrate and having first andsecond openings through which the first diffusion layer formed betweenthe first and second regions is exposed; a first electrode line formedon the insulating layer and connected to the first diffusion layerthrough the first opening; and a second electrode line connected to thesubstrate region through the second opening.

According to a third aspect of the present invention for achieving theobjects, there is provided a method of fabricating a submount substratefor mounting a light emitting device, comprising the steps of: preparinga substrate doped with first polar impurities; injecting and diffusingsecond polar impurities having the polarity different from that of thefirst polar impurities into top and bottom surfaces of the substrate toform first and second diffusion layers; forming a mask layer on the topsurface of the substrate such that a part of the first diffusion layeris exposed therethrough; etching the exposed first diffusion layer andthe substrate to form a groove, and then removing the mask layer;forming an insulating layer on the groove and the first diffusion layerexposed by removing the mask layer therefrom; etching the insulatinglayer formed on the first diffusion layer and the groove to form a firstcontact region through which the first diffusion layer is exposed and asecond contact region through which the substrate is exposed; andforming a first electrode line connected to the first diffusion layerthrough the first contact region and a second electrode line connectedto the substrate through the second contact region.

According to a fourth aspect of the present invention for achieving theobjects, there is provided a method of fabricating a submount substratefor mounting a light emitting device, comprising the steps of: preparinga substrate doped with first polar impurities; injecting and diffusingsecond polar impurities having the polarity different from that of thefirst polar impurities into top and bottom surfaces of the substrate toform first and second diffusion layers; forming mask layers,respectively, on the top and bottom surfaces of the substrate, removingpart of the mask layer formed on the top surface of the substrate toform a first region to which a light emitting diode is bonded and secondregions each of which is spaced apart from the first region in anopposite lateral direction of the substrate to separate the diffusionlayer, and then removing the mask layer formed on the top surface of thesubstrate; etching the first diffusion layer and the substrate in thefirst and second regions; forming an insulating layer on the substrateincluding the etched regions; etching the insulating layer between thefirst and second regions to form first and second contact regionsthrough which the first diffusion layer is exposed; and forming a firstelectrode line connected to the first diffusion layer through the firstcontact region and a second electrode line connected to the substratethrough the second contact region.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become apparent from the following descriptions ofpreferred embodiments given in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-sectional view of a general light emitting diode;

FIGS. 2 a and 2 b are equivalent circuit diagrams of a light emittingdevice and a voltage regulator device;

FIGS. 3 a to 3 g are cross-sectional views illustrating a method offabricating a conventional PN Zener diode;

FIGS. 4 a to 4 g are cross-sectional views illustrating a method offabricating a submount substrate for mounting a light emitting deviceaccording to a first embodiment of the present invention;

FIG. 5 is a cross-sectional view of the submount substrate for mountingthe light emitting device according to the first embodiment of thepresent invention;

FIGS. 6 a and 6 b are cross-sectional views illustrating a process ofmounting a light emitting diode to the submount substrate according tothe first embodiment of the present invention;

FIGS. 7 a to 7 i are cross-sectional views illustrating a method offabricating a submount substrate for mounting a light emitting device inwhich a Zener diode having a bi-directional threshold voltagecharacteristic is integrated according to a second embodiment of thepresent invention; and

FIG. 8 is a cross-sectional view of the submount substrate for mountingthe light emitting device according to the second embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described in detail withreference to preferred embodiments given in conjunction with theaccompanying drawings.

FIGS. 4 a to 4 g are cross-sectional views illustrating a method offabricating a submount substrate for mounting a light emitting deviceaccording to a first embodiment of the present invention, and show aprocess of fabricating the submount substrate for mounting the lightemitting device in which a Zener diode capable of protecting a lightemitting device from a surge voltage or static electricity isintegrated, using a silicon bulk micromachining process.

Referring to FIG. 4 a, a substrate (300) doped with first polarimpurities is first prepared.

Preferably, the substrate (300) is a silicon substrate.

Then, on the top and bottom surfaces of the substrate (300) are injectedand diffused second impurities having the polarity different from thatof the first polar impurities to form first and second diffusion layers(310. 311). (see FIG. 4 b)

At this time, the second polar impurities can be injected and diffusedinto the top and bottom surfaces of the substrate (310) without usingany diffusion mask.

Here, the first and second diffusion layers (310. 311) refer to layersthat are diffused to a predetermined depth from the surfaces of thesubstrate (300).

Mask layers (321. 322) are then formed on the top and bottom surfaces ofthe substrate (300), respectively. Part of the mask layer (321) formedon the top surface of the substrate (300) is removed. (see FIG. 4 c)

At this time, the mask layer (321) is partially removed to expose thefirst diffusion layer (310) to the outside.

If the substrate (300) is a silicon substrate, it is preferred a siliconnitride film be used as the mask layers (321. 322), and the partialremoval of the mask layer (321) be carried out by the wet etchingmethod.

Successively, the first diffusion layer (310), which has been exposedthrough the removal of the mask layer (321), and the substrate (300)placed below the first exposed diffusion layer are etched to form agroove (330). The mask layers (321, 322) are then removed. (see FIG. 4d)

Here, the groove (330) is formed in such a manner that a wet etchingplane shown in FIG. 4 d can be obtained by performing anisotropic wetetching (by which the substrate is etched such that an etch rate of a[100] plane is high and an etch rate of a [111] plane is low if thesubstrate (300) is a silicon substrate) depending on a crystallinedirection.

Preferably, an angle between the [100] plane and the [111] plane is54.74 degrees. Further, the [111] plane thus formed can be used as amirror surface for reflecting light emitted from a side surface of thelight emitting device toward a front surface of the substrate.

An insulating layer (340) is then formed on the first exposed diffusionlayer (310) and groove (330). (see FIG. 4 e)

Further, the insulating layer (340) partially formed on the firstdiffusion layer (310) and the groove (330) is etched to form a firstcontact region (A) through which the first diffusion layer (310) isexposed and a second contact region (B) through which the substrate(300) is exposed. (see FIG. 4 f)

Finally, a first electrode line (351) connected to the first diffusionlayer (310) through the first contact region (A), and a second electrodeline (352) connected to the substrate (300) through the second contactregion (B) are formed. (see FIG. 4 g)

In the submount substrate, thus configured, for mounting the lightemitting device, the substrate (300) doped with the first polarimpurities and the first diffusion layer (310) doped and diffused withthe second polar impurities having the polarity different from that ofthe first polar impurities are constructed into a PN Zener diode.

Furthermore, electrodes of the light emitting device are bonded to thefirst and second electrode lines (351. 352) of the submount substratesuch that the light emitting diode is flip-chip bonded to the submountsubstrate.

Referring now to FIG. 5, the submount substrate for mounting the lightemitting device according to the first embodiment of the presentinvention includes the substrate (300) doped with the first polarimpurities; the first diffusion layer (310) formed by causing the secondpolar impurities having the polarity different from that of the firstpolar impurities to be injected and diffused into the substrate (300)and then divided into two parts by means of a substrate region with nodiffusion region formed thereon; the insulating layer (340) formed on atop surface of the substrate (300) and having a first opening (341 a)through which part of one divided region of the first diffusion layer(310) is exposed and a second opening (341 b) through which part of thesubstrate region with no diffusion region formed thereon is exposed; thefirst electrode line (351) formed on a top surface of the insulatinglayer (340) and connected to the first diffusion layer (310) through thefirst opening (341 a); and the second electrode line (352) connected tothe substrate region through the second opening (341 b).

Preferably, the substrate region with no diffusion region formed thereonis constructed by the groove (380) formed by etching the substrate up toa predetermined depth.

The submount substrate is further comprised of the light emitting diodewhich is flip-chip bonded to the first and second electrode lines (351.352).

Preferably, sidewalls of the groove (380) are inclined.

Still furthermore, if there is a height difference between anN-electrode and a P-electrode of the light emitting diode, the thicknessof the insulating layer is determined by the height difference betweenthe electrodes of the light emitting diode. Therefore, the lightemitting diode can be bonded to the submount substrate without anyinclination thereto to enable to improve bonding reliability.

If there is a height difference between the electrodes of the lightemitting diode bonded to first and second electrode lines, theinsulating layer is formed with a thickness corresponding to the heightdifference between the electrodes of the light emitting diode, so thatthe light emitting diode can be bonded to submount substrate in ahorizontal equilibrium state.

FIGS. 6 a and 6 b are cross-sectional views illustrating a process ofmounting a light emitting diode to a submount substrate for mounting thelight emitting device according to the first embodiment of the presentinvention. First, solder metal pads (361, 362) are formed on the firstand second electrode lines (351, 352) of FIG. 4 g, respectively. (seeFIG. 6 a)

Then, electrodes (401, 402) of the light emitting diode (400) are bondedon top surfaces of the solder metal pads (361, 362), respectively, bymeans of a flip-chip bonding process. (see FIG. 6 b)

FIGS. 7 a to 7 i are cross-sectional views illustrating a method offabricating a submount substrate for mounting a light emitting device inwhich a Zener diode having a bi-directional threshold voltagecharacteristic is integrated according to a second embodiment of thepresent invention. Herein, a PNP (or NPN) Zener diode is used as theZener diode having the bidirectional threshold voltage characteristic.

First, a substrate (300) doped with first polar impurities is prepared.(see FIG. 7 a)

Preferably, the substrate (300) is a silicon substrate.

Then, on the top and bottom surfaces of the substrate (300) are injectedand diffused second impurities having the polarity different from thatof the first polar impurities to form first and second diffusion layers(310. 320). (see FIG. 7 b)

Successively, mask layers (510. 520) are formed on the top and bottomsurfaces of the substrate (300), respectively. Some parts of the masklayer (510) formed on the top surface of the substrate (300) are removedto form a first region (a region “F”) to which a light emitting diode isto be bonded, and second regions (regions “E”) each of which is spacedapart from the first region in an opposite lateral direction of thesubstrate to separate the diffusion layer. (see FIG. 7 c)

To this end, part of the mask layer (510) should be removed up to asmuch a depth as the diffusion layer can be etched to a certain degree toallow the diffusion layer to be separated.

After the first and second regions have been formed, the mask layer(510) is then removed.

Further, the first diffusion layer (310) and the substrate (300) in thefirst and second regions are etched. (see FIG. 7 d)

Preferably, each second region is etched in the form of a V-cut groove.

Then, an insulating layer (520) is formed on the substrate (300)including the etched regions. (see FIG. 7 e)

The insulating layer (520) is further etched between the first andsecond regions to form first and second contact regions (G1, G2) throughwhich the first diffusion layer (310) is exposed. (see FIG. 7 f)

Furthermore, a first electrode line (531) connected to the firstdiffusion layer (310) through the first contact region (G1) and a secondelectrode line (532) connected to the substrate (300) through the secondcontact region (G2) are then formed. (see FIG. 7 g)

Finally, solder metal pads (561. 562) are formed on the first and secondelectrode lines (531. 532), respectively. Electrodes (701. 702) of alight emitting diode (700) are bonded to the solder metal pads (561.562), respectively, by means of a flip-chip bonding process. (see FIGS.7 h and 7 i)

Referring to FIG. 8, the submount substrate for mounting the lightemitting device according to the second embodiment of the presentinvention comprises the substrate (300) doped with the first polarimpurities; the first diffusion layer (310) formed by causing the secondpolar impurities having the polarity different from that of the firstpolar impurities to be injected and diffused into the substrate (300)and then divided into two parts by the first region with no diffusionregion formed thereon, each divided diffusion layer in turn beingdivided into two parts by the second region with no diffusion regionformed thereon; the insulating layer (520) formed on a top surface ofthe substrate (300) and having the first and second openings (521 a. 521b) through which the first diffusion layer (310) formed between thefirst and second regions is exposed; the first electrode line (531)formed on the insulating layer 520 and connected to the first diffusionlayer through the first opening (521 a); and the second electrode line(532) connected to the substrate region through the second opening (521b).

Preferably, the first and second regions with no diffusion region formedthereon are constructed by grooves (390. 391 a. 391 b) formed by etchingthe substrate up to a predetermined depth.

More preferably, the second regions are etched in the forms of V-cutgrooves (391 a. 391 b).

Furthermore, the submount substrate for mounting the light emittingdevice includes a light emitting diode that is flip-chip bonded to thefirst and second electrode lines (351. 352).

As described above, according to the present invention, since a submountsubstrate for mounting a light emitting device in which a Zener diodedevice is integrated can be fabricated by means of a silicon bulkmicromachining process without using a diffusion mask, some processesrelated to the diffusion mask can be eliminated. Accordingly, there isan advantage in that the manufacturing costs can be reduced.

Furthermore, there is another advantage in that since a light emittingdevice can be flip-chip bonded directly to a submount substrate for alight emitting device in which a Zener diode device is integrated, aprocess of packaging the light emitting device and the voltage regulatordevice can be simplified.

Still furthermore, if there is a height difference between anN-electrode and a P-electrode of a light emitting diode, the thicknessof an insulating layer can be determined by the height differencebetween the electrodes of the light emitting diode. Therefore, there isa further advantage in that since the light emitting diode can be bondedto the submount substrate without any inclination thereto, bondingreliability can be improved.

Although the present invention has been described and illustrated inconnection with the preferred embodiments of the present invention, itis not limited thereto. It will be apparent to those skilled in the artthat various modifications and changes may be made thereto withoutdeparting from the technical scope and spirit of the invention.Therefore, the true scope of the present invention should be defined bythe technical spirit of the appended claims.

1. A method of fabricating a submount substrate for mounting a lightemitting device, comprising the steps of: preparing a substrate dopedwith first polar impurities; injecting and diffusing second polarimpurities having the polarity different from that of the first polarimpurities into top and bottom surfaces of the substrate to form firstand second diffusion layers; forming a mask layer on the top surface ofthe substrate such that part of the first diffusion layer is exposedtherethrough; etching the exposed first diffusion layer and thesubstrate to form a groove, and then removing the mask layer; forming aninsulating layer on the groove and the first diffusion layer exposed byremoving the mask layer therefrom; etching the insulating layer formedon the first diffusion layer and the groove to form a first contactregion through which the first diffusion layer is exposed and a secondcontact region through which the substrate is exposed; and forming afirst electrode line connected to the first diffusion layer through thefirst contact region and a second electrode line connected to thesubstrate through the second contact region.
 2. The method as claimed inclaim 1, wherein the groove has inclined sidewalls.
 3. The method asclaimed in claim 1, wherein the substrate is a silicon substrate.
 4. Themethod as claimed in claim 1, further comprising the step of flip-chipbonding a light emitting diode to the first and second electrode linesafter forming the first and second electrode lines.
 5. The method asclaimed in claim 1, wherein the step of etching the exposed firstdiffusion layer and the substrate to form a groove is to perform a wetetching process to etch the first diffusion layer and a substrate regionand to form a groove.
 6. A method of fabricating a submount substratefor mounting a light emitting device, comprising the steps of: preparinga substrate doped with first polar impurities; injecting and diffusingsecond polar impurities having the polarity different from that of thefirst polar impurities into top and bottom surfaces of the substrate toform first and second diffusion layers; forming mask layers,respectively, on the top and bottom surfaces of the substrate, removingparts of the mask layer formed on the top surface of the substrate toform a first region to which a light emitting diode is bonded and secondregions each of which is spaced apart from the first region in anopposite lateral direction of the substrate to separate the diffusionlayer, and then removing the mask layer formed on the top surface of thesubstrate; etching the first diffusion layer and the substrate in thefirst and second regions; forming an insulating layer on the substrateincluding the etched regions; etching the insulating layer between thefirst and second regions to form first and second contact regionsthrough which the first diffusion layer is exposed; and forming a firstelectrode line connected to the first diffusion layer through the firstcontact region and a second electrode line connected to the substratethrough the second contact region.
 7. The method as claimed in claim 6,wherein in the step of etching the first diffusion layer and thesubstrate in the first and second region, each second region is etchedin the form of a V-cut groove.
 8. The method as claimed in claim 6,wherein in the step of etching the first diffusion layer and thesubstrate in the first and second region, the first region is etched inthe form of a groove whose sidewalls are inclined.
 9. The method asclaimed in claim 6, wherein the substrate is a silicon substrate. 10.The method as claimed in claim 6, further comprising the step offlip-chip bonding a light emitting diode to the first and secondelectrode lines after forming the first and second electrode lines.